Certain types of database queries include sub-queries where a column may be scanned a large number of times. In situations which involve these sub-queries, the associated database query may suffer from performance degradation. Conventional techniques for reducing a number of column scans include maintaining a plurality of secondary indexes. However, maintenance of these secondary indexes can result in a serious performance impact on write operations because each write operation may need to update all of the secondary indexes. Thus, these conventional techniques burden database writing and are not feasible for use with, for example, a column store database having a row level versioned (RLV) architecture.
In the drawings, like reference numbers generally indicate identical or similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears.